Method of refrigerating food



June 20, 1950 H. w. PROTZELLER METHOD OF REFRIGERATING FOOD PRODUCTS 3 Sheets-Sheet 1 Filed Oct. 7, 1943 (INN OQ wm. NNNW NN km uAlll :-llri H. W. PROTZELLER METHOD OF REFRIGERATING FOOD PRODUCTS June 20, 1950 3 Sheets-Sheet 2 Filed 001'.. 7, 1943 .7-511 l JIWINUAIJI June 20, 1950 H. w. PROTZELLER 2,511,875

METHOD 0F REFRIGERATING FOOD PRODUCTS Filed Oct. 7, 1943 5 Sheets-Sheet 5 eZZef' Y Patented June 20, 1950 4.UNITED "STATES ceri-.refe

.Harry Pplizellfy Fairmont-Minn assigner 0f one-half to Arthur Wm. Nelson, Park -RidgefIlL Application October 7,

11a claims.

`This invention relates-cto improvements in method-of yrefrigeratingwfood products and kit consists of the matters-hereinafter described and more particularly vpointed out :intheapf pended claims.

One of the objects 4of: thel invention is to provide a refrigeratedfood product lin'vvhich there' is retained in the :foodcproductto a greater-.extent -f than heretofore, the Iflavor',v 'color, essential minerals, vitamins and volume.

Itis also an object ofthe present invention to provide a method of refrigerating food products that retains, to an extent `greater than heretofore possible, the fiavor, colonessential minerals, vitamins and volume of the .food products.

Another object of the invention is'to provide a method of this kind 'that may be carried out by the use of an imperforate food product container adapted to be surrounded by a low temperature medium and so constructed that heat units are removed from the products by being absorbed by said medium through the outer skinor covering of the container.

A further object of the invention isto provide a method of this' kind adaptedv to be 'carried out by an aircraft into a ylovv temperaturehigh altitude air and wherein heat units are transmitted through the outer covering of container to atmosphere to thus accomplish the refrigerating operation.

Again, it 'is an object of the invention to `provide an improved method of freezing food products which is fast and economical and leaves said products in excellent condition for use.

The above mentioned objects ofthe invention, as Well as others, together With the several advantages thereof will more fully appear as the specification proceeds.

In the drawings:

Fig. 1 is a vertical longitudinal sectionalyiew through one form of means for carryingout the invention, as taken on the line I-I of Fig. Grand on a scale enlarged thereover.

Fig. 2 is a transverse vertical sectional view through the improved means as taken on the line 2--2 of Fig. 1 and 'on-a scale enlarged ov'erthat of Fig. 1.

Fig. 3 is another transverseverticalsectional View through said vmeans on the scale of Fig. '2 as taken on the Vline 3-'3 of Fig. 1.

Fig. 4 is a horizontal sectional View through a part of the improved means'as taken on the line 4--4 of Fig. 1.

Fig. 5 is a transversevertical sectional view through a part ofthe means shown in Fig. 1 astaken on the line5-'5 ofFigJ 1.

leisgseiaiNofSca-ez (c1. ca -17o) Fig. `iisv a vi'eWwin iront 'elevationfof tan :airplane l equipped ."'vvith theiniproved means, -When said plane is on'theground.

Fig.'7fis,a'view inisideielevatior of thefairplane InI the form shoi'wn,*'theWimproved'means is a streamlined 'hollow rbodyhavingy an'imperfo'rate outer shell or coveringforfmed for vthe.; qucl:fcon ductionpfheat units therethrough. This' body,

Whichiis :made'zto': holdpthefproductszto berefrigerated isfadapted to'l'bedetachablyiconnected:to and exteriorly carried; 'by an Aanfcraft fand it includes internally." means forV circulating xthe air vTin the bodyfbetvveen'the. .contained .p'rdu'cts and '.tl'ien into engagement with the ,finner-fsurfa'ce'iof .the covering. "Thuswhenfthe airplanezisan ightin a" highfaltit'ude, 10W temperature `aiigrthe shell iis cooled-.to .acorrsponding'lydow temperature and thecirculated air giveszupitheiheatiunitszabsorbed,

tion'ther'ethrough-to atmosphere.

VReferring rnow in detail lto .that `:embodiment of thenverition shovvn': in; the drawings andas 'appears irr Figs.' v41, :2`b and=3 lthereof, .zthegimproved m'eansiis-in the forinfof azstreamlinedfhollowpody lo preferaioiyy made gas'i a `wading Ytor nose-section Ilpan -op'en'endedfm'ain 'or intermediate Avrfood products :containing secti'on 'I2 and arrtlailirig ior tail sectionfl'B. "The'fnose fsectionfa'nd 'the mail section'. constitute closuresv for `the ionen 1Vfrontjand rear ends of thefmain or"in,teimediat.v Section. They' are zpreferably hinged fthereto whereby they maybe swung from` a'gpositionc1QSing:saide11dS:to

a position 'uncovering said., ends fof-lille, loading and' unloading fof food-products into andirom saidintermediatesection. In .the present instance the hinged-connectionvfor said n0se.and;tailsec tions -lai'e `so formedrtl'iat.said sections may :be svvung'rin `afl'iorizontal:plane about :the vertical 140 hinges l'Mande `I5 'shownfinfdottedlines in xFig. f7,

A The structuren members. .vszhighlare arguatgly spaced;Inay-'take' the form fof metal Tmbars, ar-

ranged With their flanges or stems 18. Vei.,t;e i1 ;h irg radially 'inward and with theirheads I eengaged with and secured tothe inner surface of the shell.

n Iis .desired .thatthe .Shellhave.ibgeapeciirf permittingithe'quick passage of heat units 'there- Centrally in each bulkhead is a square opening (see Fig. 2) of a considerable area and connecting said bulkheads, at the corners of the square openings therein, are longitudinally extending members 24 in the form of angle bars as best appears in Fig. 2. To increase the structural strength of the bulkheads, the front face of each bulkhead has vertical angle bars 25 xed thereto. The rear face of each bulkhead has horizontal angle bars 26 fixed thereto. These bars are arranged to bound the opening 23 in the respective bulkheads and they engage and are fixed to thevertical and horizontal anges of the longitudinal angle bars 24, before mentioned. Thus theopenings 23 in the bulkheads and the angle bars 24 define a centrally located, longitudinal chamber or passage in the main body portion I2 that extends from one end to the other thereof. With this arrangement it is to be noted also that spaces 21--21 are formed between the periphery of the various bulkheads and the internal surface of the shell or covering I1.

l The nose section has a rounded front end and it iis ared outwardly at the rear end lto match with the front open end of the intermediate or main section I2 as appears best in Fig. 1. Said nosesection includes a plurality of longitudinal ribs Ia and a shell or covering [1a that match up with the ribs I6 and shell I`1 of said main or intermediate section. The rear end of the nose section includes a bulkhead 28 which engages with and is xedrto the rear ends of the ribs Ilia in the samemanner as the bulkheads 2li-2| and 22 arevfixed to the ribs I1. Thus an annular space 29 is provided between the bulkheadr 28 and rear endof the shell I1a and whereby circulated air may pass from the rear end of the nose section I I into the spaces 21 of the section I2.

The' bulkhead or partition 28 is formed with a central opening 30 and a forwardly projecting shroud 3l and which opening and shroud are coaxial with the passageway or chamber in the main or intermediate body section. In the front end of thel shroud is located an air circulating means shown herein as a fan 32 and a driving motor 33 therefor. Instead of using a driving motor for this fan it may be driven by a propeller locatedin'advance of the nose and connected by a shaft to the fan. However, such a drive would require means for disconnecting the drive as necessary and preferably means for varying the speed of the internal propeller in accordance with the density of the atmosphere within the container.

"The trailing or tail section I3 tapers toward its rear end from its front end, which matches the open rear end of the main body section. The tail section `includes a plurality of longitudinal ribs I'Bb and a shell or covering I1b that'match with the ribs IS and covering I1 at the rear end of the intermediate section'. The front end of the tail section includesabulkheador partition 34 which engages with and is xed to the ribs Ib in the 4 same manner as the bulkheads 20, 2I and 22 are fixed to the ribs I1. Thus an annular space 35 is provided between the bulkhead and rear end of the shell I1b and whereby air may pass from the rear end of the main section I2 into the front end of the tail section I3. The bulkhead 34 is provided with a rectangular opening 36 which registers with the rear end of the chamber in said main section.

31 indicates a partition disposed toward the rear end of the tail section I3 to divide the tail section into front and rear chambers I3a and 13b respectively. A vent 38 is provided at the apex of the rear section connecting compartment I'3b with atmosphere. The partition 31 which functions as'a seal between the compartments I3a and 13b carries an axially disposed pressure equalizing tube 39 whichopens into both chambers I3a and |312. That end of the tube 39 within the chamber 13a is provided with an electrically operated valve 40 adapted to be controlled from a point remote therefrom. In said compartment I3a. is provided a casing 4I to house suitable 'i gauges whereby the pressure and the temperature existing within the member I0 as a whole may be indicated at a point remote therefrom. By the means just above mentioned the pressure and the temperature in the hollow body I0 as a E whole may be controlled from said remote point.

The main or intermediate section I2 is provided along its top median line with a fairing like hollow strut 42. An opening 43 is provided in the shell I1 in line with the bottom of the strut so that communication for air circulation is afforded between the upper portion of the main section I2 and the interior of the strut. The top end of said strut, which is closed by a plate 44 includes an outwardly extending top ange 45. It

`is through this ange 45 whereby the hollow body I!) as a whole may be detachably connected to a support adapted to be disposed in a low tem perature medium.

Primarily one or more of the hollow bodies above described is or may be carried exteriorly of an aircraft so that the same may be trans` ported to a high altitude where low temperature air exists. In Figs. 6 and 7 I have shown a four motored airplane that includes a fuselage 50, laterally extending wings 5I, operators cabin 52 and horizontal and vertical tail end rudders 53 and 54 respectively. Each wing carries nacelles 55, each enclosingy a suitable motor or engine that drives a propeller 5G.

In the present instance, two of the hollow bodies III-I0 are shown as carried exteriorly by the For purpose of balance one is disposedv plane. under each wing so as to extend in a fore and aft direction and arranged in;a plane between w the two nacelles of the associated wing so as to depend from the underside thereof. In a smaller plane, wherein only one of said bodies is to be carried thereby, it may be detachably connected yan elongated substantially horseshoe or U-shaped attaching flange 150,' the rear and open end of the hunters samefbeingfsdirected' towardthefrear Leidgenf the l `Wing. i The .crear rends 'u of s theside farms Aof this ilan'gezrare parallelasnbestfappearsin Fig.- 4 and -in the inner edge fof this flangelis a groove 6l into which 'thewfiange 45 of'thefairing strut before `mentioned: may 1befinsertedrfrom the rear end of nthe flange. Whentheange 45 is engagedin the grooveiLfasteners B2-62: are inserted into reg- .isteringz openings f in -V the :flanges 45 and 60 respectively and whereby thexbody IIJ` as a vvholel is um forgpa'ssagetherethroughy by conductiom-tofthe detachably:secured in :p1ace;ina, pendent condition.

The channel-in the main-orA intermediate section l2 as'deiinedxby the openings 23of the bulk- '6 end of' thel container. 'oIn itsfcirculation; and pasrsage' .'.through o. the: :.container, @the :faircf'lcolumn zpasseszbetweeni'aboutandzfoverethe food products 611 :fand will ,f absorb s heat awaits therefrom.: `to abe -carried outithrough-,theshroud -Sl i-ntofgthe nose section. I"Ih-us ,the'fair@contained-.inithe .body ileasi afin/hole, las. iti-passes throughi the container, .will ifabso'rb l heat uni-ts from @the foods products fandtwhich are givenzruri:.ftotthen colder shellvparts surroundingi atmosphere@ and dissipated therein. :.As the interior surface. ofthe fairing sheeti lis in communication with the interiorpfsthecbodyali) as-qawhole, by-freason off ther-opening-ll` it :adds

heads or partitions therein is adapted. to receive ,mi ,itsi surface.gtogthat,-offthelshelr mp-heatabmrban open endedcontainer-GS iof such a rectangular :crossesection that the. corners thereof have `a adaptedtobe engaged with thebulkhead or par- .tition 28o? the nosesection when the same is .closed and its rear-end is adapted to be engaged byy the bulkheadll of the ltail section when the vsame is closed. Thuswhen the container is in place'and the nose and tail sections are in the position closing the front and rear open end of the main or intermediate section, the container -is secured in'place against endwise shifting.

.The container is provided with a plurality of vertically spaced horizontallydisposed forami- 'nous shelvesiwhicharebest indicated in dotted `lines in Figs. 1 and 2. rShelves of openwork wire ,fabric or expanded metal serve the purpose.

The food product tofbe refrigerated'or frozen is preferably arrangedinthe form of unit-like packages, boxes, or baskets or cartons indicated at 61 and are Yso disposedvupon said shelvesas .to leavelongitdinal-and transverse passages or Vspaces therebetweenzas best appears in Figs. 1

and 2. y

It is to be understood that the shelves may-be loaded before `they-are-placed in the container and. into Whichthey may be slid from one end. 4The container may. beslipped into the main sectionof thebody ilil from-eitherend after the associatednose or tail section has been swung into V.the opennposition, it being assumed that said rbody' lil. asa Whole` has .been applied to the airplaneas before"` described. After the container has been placed 4in '.the main section l2, sayV from the, open rear end, .and .has been loaded with food products, `the.tail section I3 is then swung into the position closing said end of the 'main section and it is then'suitably locked in lthe' closed position.

The airplane may Vnovv take off for a flight to some selected destination and in itsiiight rises to a' high altituden Where low temperature air prevails. ""The'operator in 'fthe cabin Vt2, upon reading the temperature and pressure in the body 'l f from' the' instruments in the housing 4 I may nou/"start them'otor 33'4 "in" each nose section Il todrive the -associated"fan 32. "Each fan when driven, Will fcreate a"b'last 'of"a'ir" which will 'impinge the interiorofthe'nose section to follow the e-internal'lsurfa'ce'thereof and: pass through the openings 29 toenter'the-front end of the passage' 2l. 'f-By meansof =the front, rear andintermediate" bulkheadspr 'partitions 2l-'2l and 22, the moving-lair isidirectedinto contact with the internalf-surface-of -the'ishell- Hfito -pass out the rear endsofisaidlpassage211into-the chamber 13a :ing andgconducting purposes.

, Shoulddt -be '-indicated by` the .instruments in the housing 4 l before .'mentionedfthat lthe lpresrsure in the.- body @10 is. higher orllowerthan that :off the -surroundingfatmosphere, lthe operator in 'theicabin ofthegplane may,-,-if he desires, energize lthe valve 40 .Y to-.openvthe ftubing -39 Y so that air 'from the chambert-If3b1Wil1-'enter'or vleave the chamber I 3a and equalize the 'pressuretherein.

After the plane -i lands =at its destination, the -nose end and `the `:talla-sectionsY areV openeds and 1temporary.doorslindicatedbyithe -dottedlines 10 in Fig.j 1 garefinserted into :the lopen ends of the container togclosethe-same. The container' as a whole may be now slid endwisefoutwardly from ,either openendof-:thef mainfsectionf to,` be carfriedaway-saslby motori-truck forl coldr storage or othertdisposal. 2)1T-hereafter, another vcontainer may be inserted finto;V theV main bodysection I 2 andthe .--nose Aiand-tail `sections moved to `the :closedposition and` the` plane fis; again readyfor flight to another destination.

By means of the construction described, it is possible to use airplanes for combination purposes, because passengers, mail and express matter may be carried in the fuselage at the same time that the products are being refrigerated and carried suspended from the Wings of the airplane." However, if desired, the bodies lll-I0 may be removed from the airplane so that it may be.` used as a standard airplane only.

Thuslthe-focd-products are not only transported, but maybe processed at the same time. By reason of the simple control afforded for the internal pressures in the body l0, the food products may be regulated best to maintain the desired characteristics in the products.

When products are frozen on the earths surface by methods andmeans heretofore devised and such as are .inA general use there are certain'inherent disadvantages. This is primarily :due vto the surrounding air conditions, since during the freezing process only one of these condtions of the airis changed, i. e. the temperature, the pressure and relative density remaining the same. Hence, as the initial temperature `of the product is lowered there is a volumetric reduction in the-product due to heat contraction. -This reduction in volume continues to Within a few degrees of the freezing point. Such contrac- .tion createsfa pressure on the internal liquids and cells of the product, which forces some of the liquid, closest to the external Walls, through vthese walls. It collects on the exterior of the product in the form of moisture. Generally, this moisture has a freezing point several degrees higher than that of the solid portion of the product and hence freezes'rst. As the solid portion `freezes, expansion takes place, which causes a lof the'-taililsectionflforr'irerentrancelinto-the rear "g5 Ldisturbance.on the-exterior Wallsfthereby causing the already frozen moisture to drop off. In many food products this loss of liquid amounts to some to 12 percent of the original weight of of the product. Usually the flavoring, coloring and vitamin or mineral elements, that are extremely important in all fruits and vegetables, are contained in the liquids and are generally concentrated adjacent to the exterior walls. Therefore in freezing operations, as heretoforce practiced, not only is there a serious loss of Weight, but also a definite and important impairment in quality by loss of valuable constituents of the product.

In accordance with the teaching of the present invention it is possible to lower the pressure as the product is reduced in temperature and thus counteract the tendency ofthe product to contract. Hence, the size of the product may be maintained and the loss of weight and of vital parts of the product avoided. The end result is a frozen food 'product which is far superior to frozen food products heretofore produced and which embodies substantially the qualities of the product in its natural state. y

Because the product is within a substantially air tight chamber and because the air for cooling is constantly recirculated, the dehydration losses are low compared to those in methodsfwhere fresh cold air is constantly brought into contact with the product. Y g

While, in describing the invention, I have referred in detail to the form, arrangement and construction of the parts involved, the same is to be considered only in the illustrative sense so that I do not wish to be limited thereto except as may be specifically set forth in the appended claims.

I claim as my invention: I f

1. The process of transport refrigeration of food products which comprises conveying the food products, at high altitude where low temperatures obtain, in a closed container having an imperforate covering capable of the quick transmission of heat units therethrough, the food products in said container being in spaced relation to each other and to said covering so that an annular passage is present between the spaced food products and the covering respectively, circulating the air in the container betweenand about the spaced food products in one direction to absorb heat units therefrom and then through said passage in the other direction in a manner transferring -said absorbed heat units to and through the covering for absorption by said loW temperature external atmosphere. y

2. The process of transport refrigeration of food products which comprises conveying vthe food products, at high altitudes where low temperatures obtain, in a closedcontainer having an imperforate covering capable of the quick transmission of heat units therethrough, the food products being in an open ended chamber that is spaced inwardly from said covering so as to leave an annular passage between said covering and said chamber, causing a circulation of air in said container through said chamber and between the food products therein in one direction from one end to the other and back through said passage in the other direction toward thev rst .mentioned end of the chamber to transmit heat units absorbed from said food products to and through said covering for absorption by the low temperature externalatmosphere.

3. The process of transport refrigerationV of toad products which comprises conveying-the foodv products, at high altitudes where 10W temperatures Vand 'pressures obtain," in a closed container. having an imperforate cover capable of the quick transmission of' heat units therethrough, the food products in said container being in spaced relation to each other and to said covering so that an annular passage is present between the food products and the covering respectively,` and circulating the air in the container between andfabout the spaced food products to absorbheat units therefrom and through said passage in a manner transferring the absorbed heat unitsv to and through said covering for absorption by said low temperature external atmosphere.

4. The process of transport refrigeration of food products which comprises conveying the food products, at high altitudes where loW temperatures'and pressures obtain, in a closed container having an imperforate cover capable of the quick transmission of heat units therethrough, the food products being within an open ended chamber that is spaced inwardly from said covering so as to leave an annular passage between said covering and said chamber, and circulating the air in said container through said chamber and between the food products therein from one end to the other to absorb heat units from said products and back through said passage to the first mentioned end of the chamber to transfer the absorbed heat units to and through the covering for absorption by said low temperature external atmosphere.

5. The method of transport refrigeration of food products which comprises conveying the food products within the closed shell of a traveling carrier and at high atmospheric altitudes from a starting point to a predetermined destination distant therefrom, circulating air within the closed carrier into heat absorbing relationship to the food products interiorly of the carrier shell and thence into heat transmitting relationship to the shell of said carrier during transit, thereby conducting the heat through said shell and dissipating it to the surrounding atmosphere, thereby refrigerating the product during transit.

6. The method of transport refrigeration of food products which comprises conveying the food products within the closed shell of a traveling carrier and at high atmospheric altitudes from a starting point to a predetermined destination distant therefrom, circulating air Within the closed carrier into contact with the food products interiorly of the carrier shell and into contact with the shell of said .carrier during transit, thereby conducting the heat through said shell and dissipating it to the surrounding atmosphere, thereby refrigerating the product during transit.

7. The method of producing refrigeration of products whichl consists in placing the product to be refrigerated within a hollow shell and in spaced relation to -the interior wall surfaces of the shell; closing the shell to make it imperforate and to provide a gaseous interior, transporting the product-laden n shell, by aircraft, to and through atmospheric air at such altitudes as provides a refrigerating temperature, and whilst product-laden shell is being so transported, causing circulation of the gaseous medium within the product-laden shell so as to bring tne gaseous medium into heat exchanging relation With the product and the interior surface of the productladen shell and by conduction through the shell to thereby effect refrigeration of the product.

8. The method of. producing refrigeration ci products which consists in placing the product to be refrigerated within a hollow elongatedshell; closing the shell to make it imperforate and to provide a gaseous interior, transporting the product-laden shell, by aircraft, to and through atmospheric air at such altitudes as provides a refrigerating temperature, and whilst productladen shell is being so transported, causing longitudinal circulation of the gaseous medium within the product-laden shell so as to bring the vgaseous medium into heat exchanging relation-.with the product and the interior surface of the productladen shell and by conduction through the shell to thereby effect refrigeration of the product.

9. The method of producing refrigeration of products which consists in placing the product to be refrigerated within a hollow shell, so as to leave an annular space between the product and the interior of the shell; closing the shell to make it imperforate and to provide an interior having an air content, transporting the product-laden shell, by aircraft, to and through atmospheric air at such altitudes as provides a refrigerating temperature, and whilst product-laden shell is being so transported through the atmospheric air of refrigerating temperature, causing circulation of the air within the product-laden shell so as to bring the air into heat exchanging relation with the product and the interior surface ofthe product laden shell to thereby effect refrigeration of the product.

10. The method of producing refrigeration of products which consists in placing the product to be refrigerated within a hollow metal shell in spaced relation to each other; closing the shell to make it imperforate and to provide an interior having an air content, transporting the productladen shell, by aircraft, to and through atmospheric air at such altitudes as provides a refrigerating temperature, and whilst product-laden shell is being so transported, causing circulation of the air within the product-laden shell so as to bring the air into heat exchanging relation with the product whilst moving in one direction and into heat exchanging relation withvthe interior of the said shell whilst moving in the other direction, to thereby effect refrigeration of; the product.

1l. The method of producing refrigeration of products which consists in placing the product to be refrigerated within a hollow shell and in spaced relation to the interior wall surfaces of the shell; closing the shell to make it imperforate and to provide a gaseous interior, transporting the product-laden shell, by aircraft, to and through atmospheric air at suchaltitudes as provides a refrigerating temperature, and whilst product-laden shell is being so transported, causing circulation of the gaseous medium within the product-laden shell so as to bring. the gaseous medium into heat exchanging relation with the product and the interior surface of the productladen shell and by conduction through the shell to thereby effect refrigeration of the product, and

in reducing the pressure of the gaseous medium as the temperature of the product is reduced, so as to offset, at least in part, the tendency of the product to diminish in volume as its temperature is lowered.

12. 'Ihe method of producing refrigeration of products which consists in placing the product to be refrigerated within a hollow shell and in spaced relation to the interior Wall surfaces of the shell; closing the shell to make it imperforate and to provide a gaseous interior, transporting the product-laden shell, by aircraft, to and through atmospheric air at such altitudes as provides a refrigerating temperature, and whilst product-laden shell is being so transported, causing circulation of the gaseous medium within the product-laden shell so as to bring the gaseous medium into heat exchanging relation with the product and the interior surface of the product-laden shell and by conduction through the shell to thereby effect refrigeration of the product, and in reducing the pressure of the gaseous medium as the temperature of the product is reduced, so as substantially to maintain the original volume of the product as the temperature of the product is lowered.

13. The method of producing refrigeration of products which consists in placing the product to be refrigerated within a hollow shell and in spaced relation to the interior wall surfaces of the shell; closing the shell to make it imperforate and to provide a gaseous interior, transporting the product-laden shell, by aircraft, to and through atmospheric air at such altitudes as provides a refrigerating temperature, and whilst product-laden shell is being so transported, causing circulation of the gaseous medium within the product-laden shell so as to bring the gaseous medium into heat exchanging relation with the product and the interior surface of the productladen shell and by conduction through the shell to thereby effect refrigeration of the product, and in reducing the pressure of the gaseous medium as the temperature of the product is reduced so as to prevent a reduction in the volume of the product as its temperature of the product is lowered.

HARRY W. PROTZELLER..

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS- Number Name Date 1,702,194 Bosch Feb. 12, 1929 1,907,048 Midgeley, Jr July 4, 1933 1,992,941 Fowler Mar. 5, 1935 2,109,002 Warren Feb. 22, 1938 2,184,954 Conn Dec. 26, 1939 2,203,406- Dempsey, Jr. June 4, 1940 2,259,803 Cumming Oct. 21, 1941 2,285,946 Kalischer June 9, 1942 

